PVP-CONTAINING SOLUTIONS FOR ANALYSIS OF DIVALENT CATION-DEPENDENT NMDA RESPONSES IN XENOPUS OOCYTES

The electrophysiological analysis of Ca2+-conducting ion channels in X enopus oocytes is difficult due to secondary intracellular effects ind uced by Ca2+. In the presence of polyvinylpyrrolidone (PVP) membrane c urrents can be recorded in nominally divalent cation-free solutions. T he Ca2+-permeable recombinant NMDA receptors of the NR1/NR2A subtype w ere used as assay system and the results show that PVP has no effect o n NMDA receptor-induced currents. Ca2+ and Ba2+ depress NMDA-induced c urrents at submillimolar concentrations probably by interfering with t he Na+/K+ flux. This block is fully reversible as also observed for Mg 2+ but shows in contrast no pronounced voltage dependence. PVP-contain ing solutions may be useful for the analysis of divalent cation-depend ent ion channels.